Wearable and flexible/stretchable strain sensors are widely used for motion monitoring. This paper reports a stretchable strain sensor with enhanced thermal management, achieving a 32% drop in saturated temperature. The sensor uses a thermoplastic polyurethane-boron nitride nanosheets layer for heat dissipation and a porous electrospun fibrous thermoplastic polyurethane membrane for thermal insulation. In-situ testing demonstrates dynamic operational temperature fluctuation, and cytotoxicity tests confirm biocompatibility.